Attachment plate

ABSTRACT

An attachment plate for securing a roof membrane to a roof deck includes a generally planar contact surface and at least one aperture for receiving a fastener for securing the plate to the deck with the membrane therebetween. An integrally formed, rolled collar surrounds the aperture to enhance the strength of the plate in the area adjacent the fastener. One or more stress relievers may also be formed at selected locations on the plate to provide sites for controlled deformation of the plate in the event extreme forces are exerted on the plate and the membrane, such as by heavy wind loads.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional Application No.61/220,788 filed Jun. 26, 2009. The disclosure of which is incorporatedin its entirety by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to attachment plates for securing a membrane to aroof.

2. Background Art

Attachment plates have been used previously to attach membrane sheets tosubstrates such as a roof deck. The attachment plate is typically agenerally planar sheet metal plate including one or more openings whichaccommodate a conventional fastener. The attachment plates are placedatop the membrane when the membrane is laid over the roof deck, andfasteners are inserted through openings in the plates, through themembrane, and into the roof deck to secure the plate and the membrane tothe roof deck.

The attachment plates, which are typically circular in shape, areinstalled at the perimeter and corner areas of each of the sheets of themembrane utilized on a particular deck. Attachment sheets are alsotypically positioned at the seam of adjacent membrane sheets in a mannershown and described in U.S. Pat. No. 6,952,902, issued Oct. 11, 2005 toRichard Yaros, and hereby incorporated by reference. In particular, FIG.6 of U.S. Pat. No. 6,952,902 illustrates, in cross section, theinstallation of an attachment plate at the seam of two membrane sheets,wherein one of the membrane sheets is secured by the attachment plateand the adjacent sheet overlaps the secured sheet, covers the attachmentplate, and, typically, is sealed by a suitable adhesive on each side ofthe attachment plate along the seam of the overlapping, adjoiningsheets.

It is desirable for the membranes to remain secured to the deck evenwhen subjected to high winds under severe weather conditions. Underthese conditions, the membrane may become partially separated from theroof deck and exposed to an uplifting force by extreme winds (e.g.greater than 75 miles per hour). It is desirable that the attachmentplate remains secured to the deck, and retain the membrane in placewithout causing the membrane to tear at the contact locations betweenthe membrane, the attachment plate, and the fastener as the membrane ispulled away from the roof deck by the uplifting wind.

It is, of course, also desirable to manufacture an attachment plate aseconomically as possible without compromising on the capability of theplate to retain the roof membrane in place under severe weatherconditions.

SUMMARY OF THE INVENTION

The present invention provides an attachment plate for securing a roofmembrane to a roof deck, the plate comprising a generally planar contactsurface, at least one aperture for receiving a fastener for securing theplate to the deck with the membrane between the deck and the contactsurface of the plate, and an integrally formed, rolled collarsurrounding the aperture to enhance the strength of the plate in thearea adjacent the fastener.

The attachment plate of the present invention may also include one ormore stress relievers positioned at selected locations on the plate forproviding a controlled deformation of the plate when it is subjected toextreme forces by the upwardly lifted membrane under severe windconditions. These stress relievers may be formed as lanced orpunched-through segments in the surface of the plate. The stressrelievers allow the plate to deform in a controlled fashion when theroof membrane is subjected to a heavy wind load and thereby absorb theenergy applied to the plate by the extreme forces exerted on theattachment plate and the membrane without tearing the plate or themembrane. A portion of the surface of the stress reliever will remainrelatively undeformed when the plate is subjected to extreme forces. Theleading edge of this relatively undeformed portion of the plate forms agripping surface which may engage the roof membrane as it is stretchedupwardly by wind forces and help restrain the membrane from furtherdisplacement and stretching.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a top view of one embodiment of the attachment plate of thepresent invention;

FIG. 2 shows a side cross sectional view of the attachment plate shownin FIG. 1;

FIG. 3A shows an enlarged view of the formed hole including oneembodiment of an integrally formed rolled collar;

FIG. 3B shows an enlarged view of the formed hole including anotherembodiment of an integrally formed rolled collar;

FIG. 4 shows an enlarged, schematic view of the through hole formed bythe first punching step in the process of the present invention;

FIG. 5 shows an enlarged, schematic view of the through hole followingthe second forming step of the process of the present invention;

FIG. 6A shows a top view of the attachment plate of the presentinvention including stress relievers in an unstressed condition;

FIG. 6B shows an enlarged side cross sectional view of the integrallyformed rolled collar for the stress plate of FIG. 6A;

FIG. 6C shows an enlarged side cross sectional view of one embodiment ofa stress reliever;

FIG. 7A shows a top view of the attachment plate of FIG. 6A illustratingthe stress relievers in a stressed condition;

FIG. 7B is an enlarged side cross sectional view of the integrallyformed rolled collar of the stress plate of FIG. 7A;

FIG. 7C is an enlarged side cross sectional view of the stress relievershown in a stressed condition;

FIG. 8 shows a side view of the attachment plate of the presentinvention installed in a roof deck in a normal unstressed condition;

FIG. 9 shows a side view of the attachment plate of the presentinvention being deformed by a roof membrane as it is separated from theroof deck by an extreme uplifting wind force;

FIG. 10A shows a top view of another embodiment of the attachment plateof the present invention including stress relievers in a stressedcondition;

FIG. 10B shows an enlarged side cross sectional view of the integrallyformed rolled collar for the stress plate of FIG. 10A; and

FIG. 10C shows an enlarged side cross sectional view of one embodimentof a stress reliever for the stress plate of FIG. 10A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1-3A illustrate an attachment plate 10 which is one embodiment ofthe present invention. Attachment plate 10 includes a generally planarcontact surface 12, an aperture 14, typically located at the center ofthe plate 10, for receiving a fastener for securing the plate atop aflexible membrane sheet on a roof deck, and an integrally formed, rolledcollar 16 defining and surrounding the aperture 14 to provide anenlarged contact surface adjacent the shaft of the fastener when theattachment plate 10 is installed on a roof deck.

When installed using an appropriate fastener, such as a metal screw, thefastener, being mounted into the roof deck, exerts a downwardly clampingforce on the attachment plate 10, urging the contacting surface 12 ofthe plate into contact with the roof membrane.

The integral rolled collar 16 provides a generally thicker contactsurface (as best shown at 34 in FIGS. 3A and 3B) surrounding andabutting the fastener, thereby effectively increasing the shear strengthof the plate when the plate is placed in a loaded condition caused bythe membrane being lifted upwardly away from the roof deck by extremewind forces. The rolled collar 16 thereby provides the same or evenincreased shear strength that was otherwise previously obtained inrelatively thicker conventional attachment plates. Thus, the attachmentplate 10 of the present invention can be fabricated from thinner sheetstock, thereby utilizing less material, but at the same time provide thesame or increased shear strength and superior performance at a lowercost.

As illustrated in two different embodiments shown in FIGS. 3A and 3B,the rolled collar 16 may be fabricated in such a way that there is aspace 30 between the lower contact surface 12 of the plate and therolled upper surface 32 of the collar 16 thereby creating an inner wall34 that has a height h and contact surface 54 greater than twice thethickness of the aluminum sheet. The shear force exerted by the shaft ofthe fastener on the plate when the membrane and plate are pulled as aresult of extreme upward wind forces is thereby distributed over alarger surface, thereby reducing the likelihood that the attachmentplate will rupture or tear along the inner wall of the aperture 14 whenthe plate is exposed to the extreme stress of such wind forces.

An aperture of about 0.47 inches is typically utilized for plates havingtwo to three inch diameters. In the rolled collar illustrated in FIGS.3A and 5, the collar 16 is formed with a space of about 0.010 to 0.070inches, and the rolled over portion 32, 52 of the collar is typicallyabout 0.06 inches. The collar is formed with suitable radii (shown as“r” in FIGS. 4-5) at the surface transition points to avoid sharp bends,and thereby provide a relatively stronger structure. In one embodiment,a radius of about 0.045-0.050 inches is formed at the transition pointsof the collar. For collars of the type shown in FIG. 3B the generallyhorizontal portion 26 of the rolled over material is typically about0.3125 inches wide, and the generally vertical portion 28 of the collaris about 0.125 inches in length. Of course, as will be appreciated bythose skilled in the art these various dimensions of the rolled collarmay be varied, as dictated by the thickness and type of materialutilized for the plate, as well as by the thickness of the membrane,size of the fastener, and other physical characteristics and performancestandards for a particular roofing system application.

In this embodiment, plate 10 also includes first and second reinforcingribs 18 and 20 comprising raised portions of the plate to furtherstrengthen the plate 10. In the illustrated embodiment, the reinforcingribs 18 and 20 are continuous and extend circumferentially around theplate between the center aperture 14 and the perimeter of the plate.However, it will be appreciated by those skilled in the art, thatvarious numbers and patterns of ribs may be employed to providestructural reinforcement to the plate 10 without departing from thespirit of the present invention.

In the illustrated embodiment, the gripping plate 10 also includes aflange 22 which extends around the perimeter of the plate 10. Theinboard portion of the flange 22 provides a portion of the generallyplanar contact surface 12 of the plate. The flange 22 may be angledslightly upwardly (when viewed in the side cross sectional view shown inFIG. 2) as the flange extends outwardly from the center of the plate,and may also include a scalloped edge (best viewed in the top view shownin FIG. 1) including a plurality of curved projections 24. The upwardlyangled, scalloped edge configuration of the flange 22 provides a largergripping surface in the event the membrane is pulled upward with respectto the roof deck and the attachment plate 10 and into contact with theinclined lower surface 26 of the flange 22 and the projections 24 at theedge of the plate.

The raised surface 26 of the flange 22 and the scallops 24 grip themembrane to limit sliding of the membrane as it is lifted away from theroof deck and the attachment plate by an extreme uplifting wind. In theembodiment shown in FIG. 1 twenty projections 24 are provided along theperimeter, with each projection having a depth of about 0.03 inches. Ofcourse, it will be appreciated by those skilled in the art that variousnumbers of projections and depths may be employed to achieve a maximalcontact surface with optimal gripping force, while minimizing thesharpness of the projections (thereby minimizing the possibility thatthe curved projections 24 on the edges of the flange cause a stretched,uplifted membrane to tear).

The upwardly projecting flange 22 typically extends at an angle, α ofabout 10-15° from horizontal. This slight elevation of the flange 22ensures that the edge of the flange does not engage or pierce themembrane when the plate 10 is secured atop the membrane in normalinstallation, but still provides a gripping edge if the membrane ispulled upward away from the roof deck under severe wind loads, therebytending to engage the uplifted membrane and prevent it from sliding ortearing under the extreme load.

In the illustrated embodiments, the attachment plate is generally round,with the aperture 14 located at the center of the plate. Each of thereinforcement ribs are also generally round in shape, since theytypically, though not necessarily, extend continuously around theaperture at the center of the plate. However, as will be appreciated bythose skilled in the art, other shapes, such as generally square, may beemployed for the plate, and other orientations and configurations may beutilized for the reinforcement ribs, as desired.

The attachment plate of the present invention is preferably stamped froma formable sheet material using a high speed stamping press, such asstraight side press Model No. 660, available from Bliss Manufacturing,of Hastings, Mich. Of course, other types of stamping presses may beutilized to facilitate the attachment plates. Continuous coil or sheetmetals, such as galvanized aluminum, galvanized steel, stainless steel,or other resilient, malleable material may be used. In one embodiment“AZ50” galvanized aluminum is utilized. Thicknesses in the range of0.022 inches to 0.039 inches (plus/minus 0.003 inches) have been foundsuitable for fabricating attachment plates for use in securingconventional membranes fabricated of polyvinyl chloride (or othersuitable synthetic rubber materials). As described above, utilization ofthe integral, rolled collar 16 according to the present invention allowsfor plates fabricated from aluminum sheet of 0.022 inch thickness toperform a well as, or better than, prior conventional attachment plateshaving thicknesses of 0.038 inches or greater. Thus, attachment plate 10of the present invention can be made stronger and/or more economicallyaccording to the present invention.

It will also be appreciated by those skilled in the art that attachmentplate of the present invention may be made from other suitable resilientformable materials, such as plastic, or metal/plastic combinations,formed by other forming methods such as press molding, injectionmolding, extrusion, etc., without departing from the spirit of thepresent invention.

In the illustrated embodiments, the attachment plate is generallycircular and in sizes having diameters of 2.375 or 2.625 inches. Aspreviously described, other sizes and shapes (such as rectangular,round, oval, etc.) may be employed, depending upon the type,thicknesses, and weight of the membrane, the type of roof deck, andother stress load conditions anticipated at a particular installation.

The reinforcing ribs in the illustrated embodiments are preferablygenerally arcuate in shape in cross section, with the rib extendingabout 0.05 inches above the contact surface of the plate. Of course,reinforcing ribs having varying heights above the contact surface of theplate, and with other cross-sectional shapes may be employed so long asthe ribs provide suitable strength and rigidity to the plate.

Referring now to FIGS. 4 and 5, the integral rolled collar 16 may beformed in a sequential stamping process. In the initial step, shown inFIG. 4, the aperture 14 is created by a punching process utilizing apunch tool which in a single operation punches a hole in the plate andthereafter extruded material from the major surface of the platesurrounding the punched hole into a generally vertically extendingcylinder 42 extending from the major surface 44 of the plate. In oneprocess of forming the collar, 16, a second forming die is then pressedinto contact with the plate with sufficient force to form the upperportions of the cylinder 42 into the desired collar shape, such as theshapes shown in FIGS. 3A and 3B. Again, as previously described, thetransitions in the collar are preferably formed with a suitable radius,r, so as to avoid sharp transition points which might weaken the collar.

As shown in FIG. 5, the displaced material 42 may be formed in such amanner that the rolled over material 52 extends outwardly from theaperture and generally parallel to the major surface 44, of the plate10, but in a spaced apart relationship to the major surface 44 therebycreating a space 50 between the rolled over upper surface 52 and themajor surface 44 of the plate. It will be appreciated that the innerwall 54 of the collar will have a height equal to at least twice thethickness of the plate, plus the height of the space 50 between theupper surface 52 and major surface 44. Thus, the height of the innerwall 54 and, therefore, the surface area brought into contact with theshank of the fastener in a loaded condition, may be effectivelyincreased by increasing the space 50 between the top portion 52 of therolled over wall and the major surface 44 of the plate. As earlierdescribed, by employing an integral rolled collar in this manner, theattachment plate 10 may be formed of relatively thinner sheet stock thanpreviously utilized in similar attachment plates while maintaining, orincreasing, the shear strength of the plate at the stress point of theabutment of the fastener shank with the aperture of the plate, therebyimproving the performance of the attachment plate under high loadconditions. Alternatively, the integral rolled collar may be utilized onplates of conventional thickness to improve the strength and performancewithout adding material to the plates.

FIG. 8 illustrates, in side cross-sectional view, an attachment plate 10according to the present invention installed atop a first membrane sheet82. A threaded fastener 84 extends through the aperture 14 in the plate,pierces membrane 82, and pierces the roof deck 86 (as well as anyoptional layer(s) of insulation placed therebetween), securing the firstmembrane sheet 82 between the attachment plate 10 and the roof deck. Asecond membrane (not shown) may be glued, sewn or otherwise secured tothe first membrane at 88, and laid over one or more attachment plates atthe edge of the first membrane 82, thereby defining a seam between thetwo roof membranes.

Referring now to FIGS. 6A-6C and 7A-7C, in another embodiment of thepresent invention, an attachment plate 60 is provided with an aperture14 for receiving a fastener, and an integral formed collar 16, asdescribed above, for increased shear strength in retaining the plate inplace relative to the fastener when the plate is under extreme load, anda series of stress relievers 66 formed at selected locations around theperimeter of the plate to provide pre-defined deformation sites on theplate 60. These stress relievers may be lanced, or completelypunched-through areas of the plate 60 which provide weakened sites thatwill allow for greater deformation of the plate at selected locationswhen the plate is subjected to extreme forces by a moving membrane thatis separated from the roof deck and is being pulled upward by highwinds. As shown in FIGS. 7A-7C and 9, this controlled deformation of theplate serves to absorb energy transmitted as a result of these extremeforces, rather than transmit the energy directly to the site of theattachment of the plate at the aperture 14, thereby reducing the stresson the plate caused by the force of the relatively static threadedfastener on the plate that is being strained out of position by theextreme wind forces. As a result, in an extreme wind condition such as ahurricane, an attachment plate configured with stress relievers 66 ismore likely to absorb the extreme wind forces without failing completely(e.g. shearing completely off as a result of the force of the fasteneron the wall of the plate at the aperture 14, or tearing out of thefastener from the roof deck) thereby keeping the membrane generallyattached to the roof deck under extreme conditions.

In particular, FIGS. 7A and 7C depict the stress relievers in a deformedstate wherein an outer portion 70 of the plate 60 has been deformedupwardly as a result of stress of the lower surface of the plate 60 bythe roof membrane 82 being pulled upwardly by an extreme force, such ashigh winds. This controlled deformation of a portion 70 of the plateallows for a controlled transmission and absorption of the energyapplied by the upwardly stretched, wind-blown membrane 82, therebylessening the stress on the remaining central portion 72 of the plate,as well as the collar 16, and the fastener 84. In addition, upondeformation of the outer portion 70 of the plate under stress, theadjacent, undeformed portion of the plate forms a gripping surface 76which may engage the roof membrane 82 as it is pulled upward by windforces and help restrain the membrane 82 from further displacement andstretching in the vicinity of the central portion 72 of the attachmentplate 60. The gripping surface 76 has a generally smooth, arcuate shapein the illustrated embodiments. Alternatively, the stress reliever canbe formed such that the gripping surface 76 is scalloped in a mannersimilar to the outer edge of the raised surface 26 to thereby provide alarger gripping surface at the undeformed portion 76 of the stressreliever in the event the attachment plate 60 is deformed by an extremeload and the gripping surface 76 moves into contact with the membrane.

Referring now to FIGS. 10A-10C, in another embodiment of the presentinvention, an attachment plate 90 may include a plurality of stressrelievers 92, each of which are lanced in a shape which includes agenerally arcuate surface extending at the radially outward edge 94 ofthe stress reliever 92, and first and second generally linear sidesurfaces 96 and 98. In the attachment plate illustrated in FIG. 10A, theoutward edge 94 is scalloped to include a plurality of projections 95.As shown in FIG. 10C, this stress relievers 92 may be formed to projectdownward from the surface of the plate 90 when the plate is in theunstressed condition.

In one embodiment, the stress reliever 92 is formed part to projectdownward at an angle sufficient that the leading-edge 94 of the stressplate engages the membrane when the attachment plate 90 is installed onthe roof deck in its unstressed condition. In this embodiment, thecontact of the leading edges 94 of the stress relievers 92 with themembrane provide an additional gripping force, supplementing thegripping force provided by the contacting surface of the flange 22. Inone embodiment, the stress relievers 92 are formed to project downwardat an angle sufficient that the stress relievers 92 and engage andcompress the membrane such that the stress relievers 92 provide theprimary gripping force for the plate 90.

The illustrated embodiments depict three stress relievers, each having agenerally arcuate shape. In the illustrated embodiments, the stressrelievers are equal in length, and are spaced at equal distances apartfrom each other about the circumference of the plate, with the spacebetween the stress relievers being equal or greater in length than thelength of an individual stress reliever. Of course, however, the number,shape, length, and placement of the stress relievers may be varied toachieve desired performance characteristics for a particular roofingsystem and environment.

It will be appreciated that the shape and position of the portions ofthe plate 70 and 76 immediately adjacent stress reliever 66 are slightlyexaggerated in FIGS. 6-9 for the sake of illustration. As will beappreciated by those skilled in the art the lanced or punched throughareas defining the stress relievers 66 may be barely detectable when theplate is in an unstressed condition. Similarly, deformation may occur atsome, but not all, of the stress reliever locations depending on thedegree and direction of the force exerted on the attachment plate by awind-blown, uplifted membrane.

Each of the disclosed embodiments of the present invention provide anattachment plate which is simple to fabricate, yet strong, lightweight,and effective to provide attachment of a roof membrane, whilesubstantially reducing or eliminating membrane tear problems experiencedwhen using previous attachment plate designs.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Rather, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing from thespirit and scope of the invention.

1. A plate for attaching a roof membrane to a roof deck, the platecomprising: a generally planar contact surface including at least oneaperture for receiving a fastener for securing the plate to a roof deckwith the membrane between the deck and the contact surface of the plateand an integrally formed, rolled collar surrounding the aperture toenhance the strength of the plate in the area adjacent the fastener. 2.The attachment plate of claim 1 wherein the rolled collar includes agenerally vertical inner wall and a generally horizontal upper surface,and wherein the inner wall has a height at least twice the thickness ofthe plate.
 3. The attachment plate of claim 1 wherein the rolled collarincludes a generally vertical inner wall and a generally horizontalupper surface, and wherein the inner wall has a height greater thantwice the thickness of the plate.
 4. The attachment plate of claim 1further including at least one stress reliever positioned at a selectedlocation on the plate for providing a controlled deformation of theplate when it is subjected to extreme forces by the upwardly liftedmembrane under severe wind conditions.
 5. The attachment plate of claim4 wherein at least one stress reliever is formed as a lanced segment inthe surface of the plate.
 6. The attachment plate of claim 4 wherein atleast one stress reliever is formed as a punched-through segment in thesurface of the plate.
 7. The attachment plate of claim 1 wherein theplate includes one aperture located at the plate, and further includingat least one reinforcing rib, each comprising a raised portion of theplate to further strengthen the plate.
 8. The attachment plate of claim7 wherein the first and second reinforcing ribs are each continuous andextend circumferentially around the plate between the center apertureand the perimeter of the plate.
 9. The attachment plate of claim 1further including a flange extending around the perimeter of the plate,and wherein the inboard portion of the flange provides a portion of thegenerally planar contact surface of the plate.
 10. The attachment plateof claim 9 wherein the flange is angled slightly upwardly as the flangeextends outwardly from the center of the plate.
 11. The attachment plateof claim 9 wherein the flange includes a scalloped edge.
 12. A plate forattaching a roof membrane to a roof deck, the plate comprising: agenerally planar contact surface including at least one aperture forreceiving a fastener for securing the plate to a roof deck with themembrane between the deck and the contact surface of the plate and atleast one stress reliever positioned at a selected location on the platefor providing a controlled deformation of the plate when it is subjectedto extreme forces by the upwardly lifted membrane under severe windconditions.
 13. The attachment plate of claim 12 wherein at least onestress reliever is formed as a lanced segment in the surface of theplate.
 14. The attachment plate of claim 12 wherein at least one stressreliever is formed as a punched-through segment in the surface of theplate.
 15. The attachment plate of claim 12 wherein at least one stressreliever is formed in a shape such that, upon deformation of the outerportion of the plate under stress, the adjacent, undeformed portion ofthe plate forms a gripping surface which may engage the roof membrane asit is pulled upward by wind forces and help restrain the membrane fromfurther displacement and stretching in the vicinity of the centralportion of the attachment plate.
 16. The attachment plate of claim 15wherein at least one stress reliever is formed such that the grippingsurface is scalloped, thereby providing a larger gripping surface at theundeformed portion of the stress reliever in the event the attachmentplate is deformed by an extreme load and the gripping surface contactsthe membrane.
 17. The attachment plate of claim 12 wherein each stressreliever is formed in a shape including a generally arcuate surfaceextending at the radially outward edge of the stress reliever, and firstand second generally linear side surfaces extending generally in theradial direction, wherein the arcuate surface is scalloped, and whereineach stress reliever is formed to project downward from the platetowards the membrane when the plate is secured to the roof deck.
 18. Theattachment plate of claim 17 wherein the radially outward edge of eachstress reliever projects downward into contact with the membrane whenthe plate is secured to the roof deck.
 19. The attachment plate of claim12 further including an integrally formed, rolled collar surrounding theaperture to enhance the strength of the plate in the area adjacent thefastener.
 20. A plate for attaching a roof membrane to a roof deck, theplate comprising: a generally planar contact surface including at leastone aperture for receiving a fastener for securing the plate to a roofdeck with the membrane between the deck and the contact surface of theplate; an integrally formed, rolled collar surrounding the aperture toenhance the strength of the plate in the area adjacent the fastener; atleast one stress reliever positioned at a selected location on the platefor providing a controlled deformation of the plate when it is subjectedto extreme forces by the upwardly lifted membrane under severe windconditions; and a flange extending around the perimeter of the plate,the inboard portion of the flange providing a portion of the generallyplanar contact surface, wherein the flange is angled slightly upwardlyas the flange extends radially outward from the center of the plate, andwherein the flange includes a scalloped edge including a plurality ofcurved projections.